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Biomedical subjects

R Snow

Publications and source records attributed to R Snow.

At least 19 recordsLinked to original sources
PubMed2002

Slow component of [V]O(2) kinetics: the effect of training status, fibre type, UCP3 mRNA and citrate synthase activity.

OBJECTIVE: In healthy individuals performing constant-load exercise at intensities above the lactate threshold a secondary rise in pulmonary oxygen uptake ([V]O(2)) occurs. [V]O(2) reaches a maximum and exhaustion rapidly prevails for a range of work rates lower than the maximal work rate achieved during a conventional rapid-incremental test. This phenomenon is called the slow component (SC) of [V]O(2) kinetics and represents an increase in [V]O(2) without an increase in work rate. Although still under debate, the magnitude of the SC is believed to be associated with the percentage of type II muscle fibres and their recruitment. In this study we investigated the relationship between the magnitude of the relative SC, citrate synthase activity, UCP2 and UCP3 mRNA levels and muscle fibre composition in both endurance-trained and recreationally active subjects. METHOD: The magnitude of the relative SC was measured in 12 endurance-trained (Tr) and 15 recreationally active (RA) male subjects. The magnitude of the relative SC was determined as the difference between the end-exercise [V]O(2) and 3 min [V]O(2) divided by the difference between end-exercise [V]O(2) and baseline [V]O(2). UCP2 and UCP3 mRNA expression in the vastus lateralis was measured by RT-PCR with beta-actin mRNA used as an internal control. These values were also normalized against cytochrome-b mRNA to control for training induced changes in mitochondria when comparing the Tr and RA groups. Type I, IIa and IIx skeletal muscle fibre composition was determined using a routine myosin ATPase histochemical staining technique. Citrate synthase (CS) activity was measured using spectrophotometric detection. RESULTS: The magnitude of the relative SC of the Tr group had the highest correlation with citrate synthase activity (r=-0.90, P<0.001) and that of the RA group with [V]O(2) peak (r=-0.68, P<0.01). For the Tr group other correlations with the magnitude of the relative SC included UCP3 mRNA levels (r=0.69, P<0.05) and the percentage of type I fibres (r=-0.58, P<0.05), while for the RA group they included UCP3 mRNA (r=0.58, P<0.05) and the percentage of type IIa muscle fibres (r=0.59, P<0.05). The Tr subjects had a lower relative SC (P=0.04) and a lower expression of UCP2 (P=0.04), and UCP3 mRNA (P=0.01) than the RA subjects. When the groups were combined the magnitude of the relative SC correlated with UCP3 mRNA (r=0.70, P<0.01), percentage of type IIa muscle fibres (r=0.60, P<0.01) and [V]O(2) peak (r=-0.73, P<0.01). Additionally UCP3 mRNA correlated with the percentage of type IIa muscle fibres (r=0.63, P<0.001). CONCLUSION: Citrate synthase activity and [V]O(2) peak are indicators of aerobic fitness. The high negative correlations between the magnitude of the relative SC and citrate synthase activity and [V]O(2) peak, of the Tr and RA subjects, respectively, suggests that the magnitude of the relative SC is inversely correlated with aerobic fitness. Additionally the correlations between UCP3 mRNA and the magnitude of the relative SC for both groups individually and combined suggest that the uncoupling activity of the UCP3 protein may also influence the magnitude of the relative SC.

Adult↗
PubMed2001

Removal of dissolved organic compounds in fixed-bed columns: evaluation of low-rank coal adsorbents.

Characterisation of a range of Victorian low-rank coal (VLRC) based and commercial adsorbents under continuous flow conditions was conducted in down flow fixed-bed columns. The effect of bed depth, hydraulic loading and initial concentration of the adsorbate 4-nitrophenol (4-NP) was studied. Prediction of the performance of the columns using bed-depth/service time analysis showed good agreement with the experimental results. The VLRC-based activated carbons gave lower service times for removal of 4-NP compared with the coconut-based commercial activated carbon Picactif. However, they showed comparable efficiency in terms of bed volumes treated and carbon usage rate (CUR). The VLRC-activated power station char (APSC) showed the lowest CUR of 0.57 g/L in comparison with 0.62 and 3.61 g/L exhibited by the commercial carbons Picactif and Hydraffin, respectively. The power station char (PSC) and Auschar gave poor CUR of 11.23 and 75.36 g/L, respectively. Three adsorbents were evaluated for the removal of natural organic matter (NOM) from aqueous solution. The breakthrough behaviour indicated that the pore size distribution of the adsorbents is an important physical characteristic for the adsorption of the NOM. There was a non-adsorbable fraction of the NOM that was a function of the type of adsorbent. In the presence of NOM, Picactif gave longer service time for the removal of 4-NP compared with APSC. consistent with the trend obtained in the absence of NOM. However, lower breakthrough times (at 10% C0) of 44 and 47% were obtained for APSC and Picactif, respectively. Further removal (35%) of 4-NP was achieved over extended operation of the beds, however more frequent backwashing was required as a result of the biological growth exhibited in the presence of NOM.

Adsorption↗
PubMed2001

A political analysis of corporate drug donations: the example of Malarone in Kenya.

This paper describes the introduction of the Malarone Donation Programme in KENYA: Using a policy analysis approach it illustrates the political nature of donation programmes and how they are affected by a large and varied group of national, regional and international stakeholders, with different levels of influence and experience. The paper shows that interaction between these different groups may affect the development and implementation of the donation programme. It ends by raising some more general questions about public/private partnerships and corporate donation programmes, and their potential impact on national drug policies.

Antimalarials↗
PubMed2001

Amino acids and endurance exercise.

Although skeletal muscle is capable of oxidizing selected amino acids, exercise in the fed and carbohydrate-replete condition results in only a small increase in amino acid utilization. Nevertheless, it may be important to increase the dietary protein requirements of active individuals. There is ongoing debate as to whether the amino acids for oxidation are derived from the free amino acid pool, from net protein breakdown, or a combination of both. There has been interest in the potential ergogenic benefits of amino acid ingestion; however, BCAA ingestion does not appear to affect fatigue during prolonged exercise, there is little support from controlled studies to recommend glutamine ingestion for enhanced immune function, and although glutamine stimulates muscle glycogen synthesis, its addition to carbohydrate supplements provides no additional benefit over ingestion of carbohydrate alone.

Amino Acids↗
PubMed2001

Creatine transporter protein content, localization, and gene expression in rat skeletal muscle.

The present study examined the gene expression and cellular localization of the creatine transporter (CreaT) protein in rat skeletal muscle. Soleus (SOL) and red (RG) and white gastrocnemius (WG) muscles were analyzed for CreaT mRNA, CreaT protein, and total creatine (TCr) content. Cellular location of the CreaT protein was visualized with immunohistochemical analysis of muscle cross sections. TCr was higher (P < or = 0.05) in WG than in both RG and SOL, and was higher in RG than in SOL. Total CreaT protein content was greater (P < or = 0.05) in SOL and RG than in WG. Two bands (55 and 70 kDa) of the CreaT protein were found in all muscle types. Both the 55-kDa (CreaT-55) and the 70-kDa (CreaT-70) bands were present in greater (P < or = 0.05) amounts in SOL and RG than in WG. SOL and RG had a greater amount (P < or = 0.05) of CreaT-55 than CreaT-70. Immunohistochemical analysis revealed that the CreaT was mainly associated with the sarcolemmal membrane in all muscle types. CreaT mRNA expression per microgram of total RNA was similar across the three muscle types. These data indicate that rat SOL and RG have an enhanced potential to transport Cr compared with WG, despite a higher TCr in the latter.

Animals↗
PubMed2000

Petrochemical exposure and menstrual disturbances.

BACKGROUND: An exploratory, cross-sectional retrospective study was conducted to examine the effects of benzene exposure on menstrual problems. METHODS: The study was based on a survey administered to over 3,000 women who worked in a large petrochemical company in Beijing, China. An abnormal menstrual cycle length (AMCL), defined as an average menstrual cycle length of greater than 35 days or less than 21 days, is the major outcome of interest. RESULTS: After 7 years of benzene exposure, the adjusted odds ratio of having AMCL for each additional 5 years of exposure was 1.71 (95% CI 1.27-2.31). Feeling stressed at work was also an important predictor. CONCLUSIONS: This study suggests a significant association of benzene exposure and perceived stress with menstrual disturbance. A prospective study is needed to confirm this finding.

Adult↗
PubMed2000

Integration of prevention and care of sexually transmitted infections with family planning services: what is the evidence for public health benefits?

It has been widely believed that, by combining the services for preventing and treating sexually transmitted infections (STI) with those for family planning (FP), STI coverage would increase and the combined service would be of higher quality and more responsive to the needs of women. So far, there is little concrete evidence that integration has had such an impact. Besides the absence of documentation, a clear definition of integration is lacking. We therefore carried out a comprehensive review of concrete experiences with integrated services, and present a summary of our findings in this article. The results indicate that the tasks of STI prevention, such as education for risk reduction and counselling, have been integrated into family planning services much more frequently than the tasks of STI diagnosis and treatment. Some STI/FP integration efforts appear to have been beneficial, for instance when the integration of STI/HIV prevention had a positive impact on client satisfaction, and on the acceptance of family planning. Less clear is whether STI prevention, when concentrated among traditional FP clients, is having a positive impact on STI risk behaviours or condom use. A few projects have reported increases in STI caseloads following integration. In some projects, FP providers were trained in STI case management, but few clients were subsequently treated.

Delivery of Health Care, Integrated↗
PubMed1999

Balancing effectiveness, side-effects and work: women's perceptions and experiences with modern contraceptive technology in Cambodia.

This community-based study presents the results of 17 focus-group discussions primarily among poor married women of reproductive age in urban and rural Cambodia regarding their experiences with modern contraceptive methods and their preferences for different technical attributes, including effectiveness, mode of administration, secrecy and rapid return of fertility. Key findings indicate that women who use modern contraceptive technologies desire highly effective methods of birth control. Cambodian women are primarily interested in longer-acting methods, view weight gain positively and are less concerned about a rapid return to fertility upon discontinuation of a method or secrecy from their partners. Women report a high level of side-effects as well as a high level of individual variation between side-effects and each modern contraceptive method used. Women with more knowledge and experience of modern contraceptive technologies alter their preference for highly effective methods based on a method's perceived suitability. Specifically, women may switch from a modern method associated with negative side-effects to a lesser effective traditional method, either to take a break from unwanted side-effects or discontinue modern methods altogether, if another suitable method is unavailable. These and other findings point to the need for greater development and choice of contraceptive methods with different technical attributes; improved information that clearly and simply describes how each method works within a women's body and its expected side-effects; improved access to reproductive health services; and improved assessment of women's underlying burden of reproductive illness not directly associated with modern contraceptives.

Adult↗
PubMed1998

Norplant as a contraceptive device in Enugu, eastern Nigeria.

This paper is an evaluation of acceptability and use-experience with the contraceptive device Norplant at the University of Nigeria Teaching Hospital, Enugu, Eastern Nigeria. Over a period of 36 months, 173 women (8% of the clinic population) accepted the implant. Use of Norplant was concentrated among high-parity women, and the proportion of Norplant users was highest among women aged 30-34 years. Comparing Norplant and IUD users, we found Norplant users to be significantly less highly educated with < 1% of Norplant users having tertiary education compared to 25% of new IUD users. The continuation rate with Norplant was 89% at three years, suggesting this method has the potential for improving the low contraceptive prevalence in this region.

Age Distribution↗
PubMed1994

Thermoregulatory response to wearing encapsulated protective clothing during simulated work in various thermal environments.

This investigation assessed the thermoregulatory impact of performing simulated tasks normally encountered during chemical accident clean-up while wearing chemical protection clothing under various representative thermal loads. A Drager 500 (D) suit was worn with a self-contained breathing apparatus (SCBA) external to the suit, while both a Trelleborg Trellchem Super Extra (T) and a James North MZ500 (J) suit required the SCBA to be worn inside the suit. The D suit was unventilated, while the T and S suits were ventilated with the subject's exhaled air. The T suit also was ventilated via a 2 L/min flow of air from the SCBA. Subjects were six firefighters. Each simulation lasted for 30 minutes and involved tasks such as drum rolling, drum carrying, walking, and hose dragging. The trials were conducted at 11.3, 17.1, and 23.8 degrees C WBGT. The overall mean peak heart rate was 128.1 +/- 2.80 breaths/min and was elicited while performing lifting tasks. Nonsignificant differences (p > 0.05) were observed for both the average heart rate and sweat rate. Mean skin temperature, mean body temperature, and temperature within the suit cavity were significantly higher when wearing the D suit compared to wearing T or J suits; differences between the T and J suits were nonsignificant. Suit type did not significantly affect rectal temperature, which also failed to exceed the American Council of Governmental Industrial Hygienists' (ACGIH) standard of 38.0 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Magnetic resonance imaging of body fat of athletes compared with controls, and the oxidative metabolism of estradiol.

The extent of 2-hydroxylation of estradiol (E2), which yields a non-estrogenic metabolite (2-OHE1), increased significantly with decreasing subcutaneous fat (ScF)/total volume percent (TV%) and total fat (TF)/TV% evaluated by magnetic resonance imaging (MRI) for five athletes during low- and high-intensity training, and four controls. The increase in 2-hydroxylation with decreasing adiposity was associated with anovulation and amenorrhea among the athletes.

Adipose Tissue↗
PubMed1991

Patterns and severity of conduction abnormalities in Guillain-Barré syndrome.

Whether the conduction abnormalities and lesions underlying them are randomly distributed throughout the peripheral nervous system (PNS) or certain regions are selectively more vulnerable to attack is an unresolved question in Guillain-Barré syndrome (GBS). To examine this question, 15 cases of GBS were comprehensively examined using electrophysiological techniques which allowed close examination, quantitation and comparison of conduction abnormalities in motor and sensory fibres of the upper limb between the spinal cord and the distal extremities of the nerve fibres. Comparison of these studies with results expected in a model where the chances of conduction failure were uniformly distributed led to the conclusion that conduction slowing and block were not uniformly distributed in most cases. Conduction block was maximal in the terminal segment distal to the wrist and to a lesser extent both conduction block and conduction slowing were disproportionately greater across the elbow and in the axillary to spinal root segments in over one half of the cases. These findings support the hypothesis that certain regions, perhaps because of relative deficiencies of the blood-nerve barrier, may be more vulnerable in GBS than other regions.

Electric Stimulation↗